1. Field of the Invention
The present invention relates to a fan blade containment system for use with an aircraft turbofan engine. An important requirement in modern aircraft turbofan engines in commercial service is that they retain fan blades or fan blade pieces which may break off during engine operation. Fan blade failure can occur for a variety of reasons, but is commonly caused when a bird, hailstone or any other foreign object strikes the engine fan while the engine is in operation. If a fan blade or blade fragment is not retained by a suitable containment system, the blade or blade fragment--which travels at a high velocity upon failure--can cause serious damage to parts of the aircraft. It is therefore necessary to provide some containment system near the engine fan for retaining any blade or blade fragments which break off the engine fan during operation. Such a containment system should be provided near the point where fan blade failure will cause the blade or blade fragment to travel.
2. Description of the Related Art
Fan blade containment systems have been previously proposed for use in turbofan engines. The objective of such containment systems has been to provide adequate retention of fan blade fragments without increasing the overall weight of the engine shroud, thereby decreasing engine performance. Certain prior art containment systems utilized a metallic honeycomb structure for retaining fan blade fragments--examples of these types of systems can be found in U.S. Pat. Nos. 3,126,149; 4,063,847; 4,377,370; 4,452,565; 4,534,698; 4,547,122; 4,666,371; 4,705,454; 5,188,505; "Development of Advanced Lightweight Systems Containment: Final Report," C. L. Stotler (N.A.S.A., May 1981) and "Containment of Composite Fan Blades: Final Report," C. L. Stotler and A. P. Coppa (N.A.S.A, July 1979). Other prior art systems show the use of a fibrous or fabric band wrapped around the interior portion of the engine shroud as a mechanism for fan blade retention--for example, U.S. Pat. Nos. 4,038,118; 4,063,847; 4,377,370; 4,411,589; 4,425,080; 4,452,565; 4,452,563; 4,534,698; 4,699,567; 4,705,454; 4,718,818; 4,818,176; 4,902,201; 4,961,685; "Development of Advanced Lightweight Systems Containment: Final Report," C. L. Stotler (N.A.S.A., May 1981) and "Containment of Composite Fan Blades: Final Report," C. L. Stotler and A. P. Coppa (N.A.S.A, July 1979). Other prior art systems disclose the use of ceramics as a part of an overall fan blade retention system--for example, U.S. Pat. Nos. 4,289,447; 4,547,122; 4,646,810; 4,818,176 and "Development of an Advanced Fan Blade Containment System," Alan D. Lane (F.A.A., August 1989).